|
To the Co-Effect of Impurity Atoms and Structure on the Dissolution of Iron and Its Low Alloys |
|
30.09.2008 г. |
|
To the Co-Effect of Impurity Atoms and Structure on the Dissolution of Iron and Its Low Alloys A. V. Plaskeev Karpov Institute of Physical Chemistry, ul. Vorontsovo Pole 10, Moscow, 103064 Russia Received April 9, 2003 Abstract — With the use of tracers, the separate effect of small nickel additions, as well as phosphorus and manganese impurities (including their combinations with sulfur) on the corrosion electrochemical behavior of active iron is studied. Nickel (2.2%) and phosphorus (only 0.07%), which are substantially more corrosion resistant than iron, are found to noticeably suppress the active dissolution of iron from its alloys, whereas the unstable manganese (0.43%) and its sulfides (in an alloy containing 0.43% Mn and 0.06% S) accelerate the dissolution. An effect similar to that of manganese is produced by a simple increase in the defectiveness of the iron crystalline structure. The largest deceleration is observed at a small surface coverage of the dissolving alloy with nickel or phosphorus, whereas the activating effect of manganese and its sulfides is accompanied by their selective transfer to the solution. With an increase in the potential, both effects decrease in magnitude. Gener-alizing these and other data on the effects of impurities and structural defects on the active dissolution of iron made us reveal the substantial effect of the metal purity and its surface defectiveness (including that induced by a potential increase) on the steady-state kinetics of the process. All the regularities of the effect theoretically follow from the crystal-chemistry concept of dissolution.
|